Indium phosphide crystal substrate

ABSTRACT

An indium phosphide crystal substrate has a diameter of 100-205 mm and a thickness of 300-800 μm and includes any of a flat portion and a notch portion. In any of a first flat region and a first notch region, when an atomic concentration of sulfur is from 2.0×10 18  to 8.0×10 18  cm −3 , the indium phosphide crystal substrate has an average dislocation density of 10-500 cm −2 , and when am atomic concentration of tin is from 1.0×10 18  to 4.0×10 18  cm −3  or an atomic concentration of iron is from 5.0×10 15  to 1.0×10 17  cm −3 , the indium phosphide crystal substrate has an average dislocation density of 500-5000 cm −2 .

TECHNICAL FIELD

The present invention relates to an indium phosphide crystal substrate.

BACKGROUND ART

W. A. Gault et al., “The Growth of High Quality III-V Crystal by the Vertical Gradient Freeze Method,” Defect Control in Semiconductors, 1990, pp. 653-660 (NPL 1) discloses a method of growing high-quality indium phosphide by the vertical gradient freeze (VGF) method. Japanese Patent Laying-Open No. 2008-239480 (PTL 1) discloses semiconductor crystals (such as GaAs crystals) composed of gallium arsenide, the semiconductor crystal having a diameter not smaller than six inches and an average dislocation density not higher than 1×10⁴ cm⁻², and further discloses semiconductor crystals preferably having average residual strain not more than 1×10⁻⁵ measured by a photoelastic method. M. Yamada, “High-sensitivity computer-controlled infrared polariscope,” Review of Scientific Instruments, Vol. 64, No. 7, July 1993, pp. 1815-1821 (NPL 2) discloses a method of measuring, by using a high-sensitivity computer-controlled infrared polariscope, small phase retardation and birefringence of a principal axis caused by residual strain in a commercially available semi-insulating gallium arsenide (111) wafer grown by the LEC method.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Laying-Open No. 2008-239480

Non Patent Literature

-   NPL 1: W. A. Gault et al., “The Growth of High Quality III-V Crystal     by the Vertical Gradient Freeze Method,” Defect Control in     Semiconductors, 1990, pp. 653-660 -   NPL 2: M. Yamada, “High-sensitivity computer-controlled infrared     polariscope,” Review of Scientific Instruments, Vol. 64, No. 7, July     1993, pp. 1815-1821

SUMMARY OF INVENTION

An indium phosphide crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the indium phosphide crystal substrate includes any of a flat portion and a notch portion. The indium phosphide crystal substrate contains any of sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of a first flat region extending over a width from the flat portion to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a first notch region extending over a width from the notch portion to a position at a distance of 2 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, when the indium phosphide crystal substrate contains the sulfur atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when the indium phosphide crystal substrate contains any of the tin atoms and the iron atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².

An indium phosphide crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the indium phosphide crystal substrate includes any of a flat portion and a notch portion. The indium phosphide crystal substrate contains any of sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. The indium phosphide crystal substrate has average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of a first flat region extending over a width from the flat portion to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a first notch region extending over a width from the notch portion to a position at a distance of 2 mm in a direction perpendicular to a curve indicating the notch portion in the main surface.

An indium phosphide crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 pin and not greater than 800 μm. A part of an outer edge of the indium phosphide crystal substrate includes any of a flat portion and a notch portion. The indium phosphide crystal substrate contains any of sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of a second flat region extending over a width from the flat portion to a position at a distance of 1 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a second notch region extending over a width from the notch portion to a position at a distance of 1 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, when the indium phosphide crystal substrate contains the sulfur atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when the indium phosphide crystal substrate contains any of the tin atoms and the iron atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².

An indium phosphide crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 pun and not greater than 800 μm. A part of an outer edge of the indium phosphide crystal substrate includes any of a flat portion and a notch portion. The indium phosphide crystal substrate contains any of sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10′⁸ cm⁻³, tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of a second flat region extending over a width from the flat portion to a position at a distance of 1 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a second notch region extending over a width from the notch portion to a position at a distance of 1 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, the indium phosphide crystal substrate has average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic plan view showing an exemplary location of a part of an outer edge where a flat portion is formed, in an indium phosphide crystal substrate according to one manner of the present invention.

FIG. 1B is an enlarged schematic plan view showing an exemplary flat portion and first and second flat regions in the indium phosphide crystal substrate according to one manner of the present invention.

FIG. 2A is a schematic plan view showing an exemplary location of a part of an outer edge where a notch portion is provided, in the indium phosphide crystal substrate according to one manner of the present invention.

FIG. 2B is an enlarged schematic plan view showing the notch portion and first and second notch regions in the indium phosphide crystal substrate according to one manner of the present invention.

FIG. 3A is an enlarged schematic cross-sectional view showing an exemplary portion of measurement of an average dislocation density in the indium phosphide crystal substrate according to one manner of the present invention.

FIG. 3B is an enlarged schematic cross-sectional view showing another exemplary portion of measurement of an average dislocation density in the indium phosphide crystal substrate according to one manner of the present invention.

FIG. 4 is an enlarged schematic cross-sectional view showing an exemplary portion of measurement of average residual strain in the indium phosphide crystal substrate according to one manner of the present invention.

FIG. 5A is a schematic vertical cross-sectional view of the inside of a manufacturing apparatus showing an exemplary method of manufacturing an indium phosphide crystal substrate according to one manner of the present invention.

FIG. 5B is a schematic horizontal cross-sectional view of a heat-insulating material and the inside of a crucible showing an exemplary method of manufacturing an indium phosphide crystal substrate according to one manner of the present invention.

FIG. 6A is a vertical schematic cross-sectional view of the inside of a manufacturing apparatus showing another exemplary method of manufacturing an indium phosphide crystal substrate according to one manner of the present invention.

FIG. 6B is a horizontal schematic cross-sectional view of a heat-insulating material and the inside of a crucible showing another exemplary method of manufacturing an indium phosphide crystal substrate according to one manner of the present invention.

FIG. 7A is a vertical schematic cross-sectional view of the inside of a manufacturing apparatus showing yet another exemplary method of manufacturing an indium phosphide crystal substrate according to one manner of the present invention.

FIG. 7B is a horizontal schematic cross-sectional view of the inside of a crucible showing yet another exemplary method of manufacturing an indium phosphide crystal substrate according to one manner of the present invention.

FIG. 8 is a schematic plan view showing still another exemplary method of manufacturing an indium phosphide crystal substrate according to one manner of the present invention.

DETAILED DESCRIPTION Problem to be Solved by the Present Disclosure

Indium phosphide disclosed in W. A. Gault et al., “The Growth of High Quality III-V Crystal by the Vertical Gradient Freeze Method,” Defect Control in Semiconductors, 1990, pp. 653-660 (NPL 1) is disadvantageously high in ratio of defects due to cracking (a crack defect ratio) in a flat portion and the vicinity thereof or a notch portion and the vicinity thereof in manufacturing of a substrate including any of the flat portion and the notch portion in a part of an outer edge (in manufacturing of a substrate with flat portion/notch portion) and in growth of an epitaxial layer on the substrate including any of the flat portion and the notch portion in a part of the outer edge (in growth of an epitaxial layer on a substrate with flat portion/notch portion).

Though “The Growth of High Quality III-V Crystal by the Vertical Gradient Freeze Method,” Defect Control in Semiconductors, 1990, pp. 653-660 (NPL 1) has discussed an average and a distribution of dislocation densities over all crystals of indium phosphide, it has not discussed an average dislocation density or average residual strain in the flat portion and the vicinity thereof or the notch portion and the vicinity thereof.

Though Japanese Patent Laying-Open No. 2008-239480 (PTL 1), “The Growth of High Quality III-V Crystal by the Vertical Gradient Freeze Method,” Defect Control in Semiconductors, 1990, pp. 653-660 (NPL 1), and M. Yamada, “High-sensitivity computer-controlled infrared polariscope,” Review of Scientific Instruments, Vol. 64, No. 7, July 1993, pp. 1815-1821 (NPL 2) have defined an average dislocation density or average residual strain over all crystals of gallium arsenide or the entire wafer, they have not discussed an average dislocation density or average residual strain in the flat portion and the vicinity thereof or the notch portion and the vicinity thereof in the indium phosphide crystal substrate.

Therefore, an object is to provide an indium phosphide crystal substrate low in ratio of defects due to cracking (crack defect ratio) in a flat portion and the vicinity thereof or a notch portion and the vicinity thereof in manufacturing of a substrate with flat portion/notch portion and in growth of an epitaxial layer on the substrate with flat portion/notch portion.

Advantageous Effect of the Present Disclosure

According to the above, an indium phosphide crystal substrate low in ratio of defects due to cracking (crack defect ratio) in a flat portion and the vicinity thereof or a notch portion and the vicinity thereof in manufacturing of a substrate with flat portion/notch portion and in growth of an epitaxial layer on the substrate with flat portion/notch portion can be provided.

Description of Embodiments of the Present Invention

Embodiments of the present invention will initially be listed and described. In order to clearly distinguish among a plurality of flat regions and notch regions, denotations as a first flat region and a first notch region or a second flat region and a second notch region are given.

[1] An indium phosphide (InP) crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the InP crystal substrate includes any of a flat portion and a notch portion. The InP crystal substrate contains any of sulfur (S) atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, tin (Sn) atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron (Fe) atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of a first flat region extending over a width from the flat portion to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a first notch region extending over a width from the notch portion to a position at a distance of 2 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, when the InP crystal substrate contains S atoms, the InP crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when the InP crystal substrate contains any of Sn atoms and Fe atoms, the InP crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻². Since the InP crystal substrate in the present manner has an average dislocation density within a prescribed range in any of the first flat region and the first notch region, it is low in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

[2] An InP crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the InP crystal substrate includes any of a flat portion and a notch portion. The InP crystal substrate contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. The InP crystal substrate has average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of a first flat region extending over a width from the flat portion to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a first notch region extending over a width from the notch portion to a position at a distance of 2 mm in a direction perpendicular to a curve indicating the notch portion in the main surface. Since the InP crystal substrate in the present manner has average residual strain within a prescribed range in any of the first flat region and the first notch region, it is low in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

[3] An InP crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the InP crystal substrate includes any of a flat portion and a notch portion. The InP crystal substrate contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of a first flat region extending over a width from the flat portion to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a first notch region extending over a width from the notch portion to a position at a distance of 2 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, when the InP crystal substrate contains S atoms, the InP crystal substrate can have an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵, and when the InP crystal substrate contains any of Sn atoms and Fe atoms, the InP crystal substrate can have an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵. Since the InP crystal substrate in the present manner has an average dislocation density and average residual strain each within a prescribed range in any of the first flat region and the first notch region, it is lower in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

[4] An InP crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the InP crystal substrate includes any of a flat portion and a notch portion. The InP crystal substrate contains any of sulfur (S) atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, tin (Sn) atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron (Fe) atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of a second flat region extending over a width from the flat portion to a position at a distance of 1 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a second notch region extending over a width from the notch portion to a position at a distance of 1 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, when the InP crystal substrate contains S atoms, the InP crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when the InP crystal substrate contains any of Sn atoms and Fe atoms, the InP crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻². Since the InP crystal substrate in the present manner has an average dislocation density within a prescribed range in any of the second flat region and the second notch region and can control the average dislocation density in a partial region located in the vicinity of an outer circumferential portion of any of the first flat region and the first notch region to be within a certain range, the InP crystal substrate is low in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

[5] An InP crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the InP crystal substrate includes any of a flat portion and a notch portion. The InP crystal substrate contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10′8 cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. The InP crystal substrate has average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of a second flat region extending over a width from the flat portion to a position at a distance of 1 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a second notch region extending over a width from the notch portion to a position at a distance of 1 mm in a direction perpendicular to a curve indicating the notch portion in the main surface. Since the InP crystal substrate in the present manner has average residual strain within a prescribed range in any of the second flat region and the second notch region and can control the average residual strain in a partial region located in the vicinity of an outer circumferential portion of any of the first flat region and the first notch region to be within a certain range, the InP crystal substrate is low in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

[6] An InP crystal substrate according to one manner of the present invention includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of the InP crystal substrate includes any of a flat portion and a notch portion. The InP crystal substrate contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of a second flat region extending over a width from the flat portion to a position at a distance of 1 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a second notch region extending over a width from the notch portion to a position at a distance of 1 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, when the InP crystal substrate contains S atoms, the InP crystal substrate can have an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵, and when the InP crystal substrate contains any of Sn atoms and Fe atoms, the InP crystal substrate can have an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵. Since the InP crystal substrate in the present manner has an average dislocation density and average residual strain each within a prescribed range in any of the second flat region and the second notch region, it is lower in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

Details of Embodiments of the Present Invention

<InP Crystal Substrate>

FIGS. 1A, 1B, 2A, and 2B show an exemplary InP crystal substrate 11 in the present embodiment. FIG. 1A is a schematic plan view showing a location of a part of an outer edge of InP crystal substrate 11 where a flat portion 11 f is formed. FIG. 1B is an enlarged schematic plan view showing flat portion 11 f and first and second flat regions 11 fr. Flat portion 11 f refers to a flat surface formed in a part of an outer edge (outer circumference) of a crystalline body and a crystal substrate for facilitating determination of a crystal orientation of the crystalline body and the crystal substrate, distinction between the front and the rear, and registration in a process. In InP crystal substrate 11 with flat portion, at least one flat portion 1 if is formed and normally two flat portions are formed, which are also called orientation flat (which is also referred to as OF below) and identification flat (which is also referred to as IF below). In InP crystal substrate 11, a plane orientation of a main surface, an off direction, an off angle, and a position of the flat portion (OF/IF) are set as desired by a client. For example, the plane orientation of the main surface is set as (100), eight off directions are set, an off angle is set to be not smaller than 0° and not greater than 20°, OF/IF positions are set as two types of a clockwise position (which is also referred to as CW below, IF being arranged at a clockwise position with respect to OF) and a counterclockwise position (which is also referred to as CCW, IF being arranged at a counterclockwise position with respect to OF), an OF length is set to be not shorter than 28 mm and not longer than 65 mm, and an IF length is set to be not shorter than 13 mm and not longer than 45 mm.

FIG. 2A is a schematic plan view showing a location of a part of the outer edge of InP crystal substrate 11 where a notch portion 11 n is provided. FIG. 2B is an enlarged schematic plan view showing notch portion 11 n and first and second notch regions 11 nr. Notch portion 11 n refers to a cut portion provided in a part of the outer edge (outer circumference) of a crystalline body and a crystal substrate for facilitating determination and alignment of a crystal orientation of the crystalline body and the crystal substrate. In InP crystal substrate 11 with notch portion, at least one notch portion 11 n is provided and normally one notch portion is provided. In InP crystal substrate 11, a plane orientation of a main surface, a shape of the notch, and a direction of a central cut of the notch are set as desired by a client. For example, the plane orientation of the main surface is set as (100), a notch is shaped by cutting off a portion having a size not smaller than 0.5 mm and not greater than 1.5 mm from the outer edge toward the center at an opening angle not smaller than 85° and not greater than 95°, and a direction of the central cut of the notch is set to a [010] direction when viewed from the center.

Embodiment I-1

Referring to FIGS. 1A, 1B, 2A, and 2B, InP crystal substrate 11 in the present embodiment includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of an outer edge of InP crystal substrate 11 includes any of flat portion 11 f and notch portion 11 n. InP crystal substrate 11 contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of first flat region 11 fr extending over a width WR from flat portion 11 f to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating flat portion 11 f in the main surface and first notch region 11 nr extending over width WR from notch portion 11 n to a position at a distance of 2 mm in a direction perpendicular to a curve indicating notch portion 11 n in the main surface, when InP crystal substrate 11 contains S atoms, InP crystal substrate 11 has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when InP crystal substrate 11 contains any of Sn atoms and Fe atoms, InP crystal substrate 11 has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻². Since InP crystal substrate 11 in the present embodiment has an average dislocation density within a prescribed range in any of first flat region 11 fr and first notch region 11 nr, it is low in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

“Being perpendicular to a curve indicating the notch portion in the main surface” in the InP crystal substrate in the present embodiment means being perpendicular to a tangential line at each point on the curve indicating the notch portion in the main surface. The “curve” here means a line not being straight at least in part and may include a straight line in part. The crack defect ratio is varied by a diameter of the InP crystal substrate, a type (S atoms, Sn atoms, or Fe atoms) or a concentration of contained atoms, or a difference in manufacturing of a substrate or growth of an epitaxial layer, and being low in crack defect ratio means a relatively low crack defect ratio so long as a diameter of the InP crystal substrate, a type (S atoms, Sn atoms, or Fe atoms) or a concentration of contained atoms, and manufacturing of the substrate or growth of an epitaxial layer are identical.

InP crystal substrate 11 in the present embodiment has a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. From a point of view of lowering in crack defect ratio also in InP crystal substrate 11 large in diameter, InP crystal substrate 11 has a diameter not smaller than 100 mm and not greater than 205 mm. From a point of view of lowering in crack defect ratio, InP crystal substrate 11 has a thickness not smaller than 300 μm and not greater than 800 μm.

A part of the outer edge of InP crystal substrate 11 in the present embodiment includes any of flat portion 11 f (FIGS. 1A and 1B) and notch portion 11 n (FIGS. 2A and 2B). By suppressing crack in flat portion 11 f and the vicinity thereof or also in notch portion 11 n and the vicinity thereof in InP crystal substrate 11, the crack defect ratio can be lowered.

InP crystal substrate 11 in the present embodiment contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. Since an average dislocation density in InP crystal substrate 11 is varied by a concentration of contained S atoms, Sn atoms, and Fe atoms, the crack defect ratio can be lowered by adjusting, at a prescribed concentration of S atoms, Sn atoms, or Fe atoms, the average dislocation density in any of the first flat region and the first notch region to be within a prescribed range. InP crystal substrate 11 is provided with N-type conductivity with increase in concentration of contained S atoms. InP crystal substrate 11 is provided with N conductivity with increase in concentration of contained Sn atoms. InP crystal substrate 11 is provided with a semi-insulating property with increase in concentration of contained Fe atoms, and at a concentration of Fe atoms not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³, the InP crystal substrate has resistivity approximately not lower than 1.0×10⁶ Ω·cm and not higher than 1.0×10⁹ Ω·cm.

From a point of view of lowering in crack defect ratio of InP crystal substrate 11 in the present embodiment in manufacturing of the substrate and in growth of an epitaxial layer on the substrate, in any of first flat region 11 fr extending over width WR from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and first notch region 11 nr extending over width WR from notch portion 11 n to a position at a distance of 2 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface, when InP crystal substrate 11 contains S atoms at the concentration above, it has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when InP crystal substrate 11 contains any of Sn atoms and Fe atoms at the concentration above, the InP crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².

From a point of view of further lowering in crack defect ratio of InP crystal substrate 11 in the present embodiment in manufacturing of the substrate and in growth of an epitaxial layer on the substrate, in any of second flat region 11 fr extending over width WR from flat portion 11 f to a position at a distance of 1 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and second notch region 11 nr extending over width WR from notch portion 11 n to the position at a distance of 1 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface, when InP crystal substrate 11 contains S atoms at the concentration above, it has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when InP crystal substrate 11 contains any of Sn atoms and Fe atoms at the concentration above, it has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².

The second flat region and the second notch region are partial regions closer to flat portion 11 f and notch portion 11 n in the first flat region and the first notch region, respectively. The second flat region and the second notch region which are parts of the first flat region and the first notch region on a side of the outer circumferential portion may be higher in average dislocation density than the first flat region and the first notch region, respectively. Since crack originates from the outer circumferential portion, a value of the average dislocation density in the second flat region affects more on the crack defect ratio. Therefore, the InP crystal substrate having the average dislocation density within the range above also in the second flat region and the second notch region which may be high in average dislocation density is lower in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

FIGS. 3A and 3B are enlarged schematic cross-sectional views showing an exemplary portion of measurement of an average dislocation density in InP crystal substrate 11 in the present embodiment. Referring to FIG. 3A, an average dislocation density in InP crystal substrate 11 is measured by using a microscope, as an average per unit area of etch pits (etch pit average density) produced in the main surface in first or second flat region 11 fr or first or second notch region 11 nr after immersion of InP crystal substrate 11 for two minutes at 25° C. in a mixture solution of 85 mass % of phosphoric acid and 47 mass % of hydrobromic acid at a volume ratio of 2:1. Etch pits, however, may not be visible in a beveled portion of the flat portion in first or second flat region 11 fr or a beveled portion of the notch portion in first or second notch region 11 nr. In this case, referring to FIG. 3B, an average density of etch pits produced by performing treatment under conditions the same as above onto a first or second flat region 11 frc in a central portion or a first or second notch region 11 nrc in a central portion exposed by grinding the main surface in first or second flat region 11 fr or first or second notch region 11 nr toward the central portion of the substrate is measured.

Though a length LR of flat portion 11 f is not particularly restricted, from a point of view of enhanced visibility and machine recognizability as well as securing a region from which a chip is taken, an OF length not shorter than 28 mm and not longer than 65 mm and an IF length not shorter than 13 mm and not longer than 45 mm are preferred. An InP crystal substrate having a diameter of four inches more preferably has an OF length not shorter than 28 mm and not longer than 38 mm and an IF length not shorter than 13 mm and not longer than 23 mm. An InP crystal substrate having a diameter of six inches more preferably has an OF length not shorter than 43 mm and not longer than 53 mm and an IF length not shorter than 25 mm and not longer than 35 mm. An InP crystal substrate having a diameter of eight inches more preferably has an OF length not shorter than 52 mm and not longer than 63 mm and an IF length not shorter than 32 mm and not longer than 43 mm.

From a point of view of enhanced visibility and machine recognizability as well as securing a region from which a chip is taken, a notch in notch portion 11 n is shaped preferably by cutting off a portion having a size not smaller than 0.5 mm and not greater than 1.5 mm from the outer edge toward the center at an opening angle not smaller than 85° and not greater than 950 and more preferably by cutting off a portion having a size not smaller than 1.00 mm and not greater than 1.25 mm from the outer edge toward the center at an opening angle not smaller than 89° and not greater than 95°, and the direction of the central cut of the notch is preferably set to a [010] direction when viewed from the center.

Embodiment I-2

Referring to FIGS. 1A, 1B, 2A, and 2B, InP crystal substrate 11 in the present embodiment includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of the outer edge of InP crystal substrate 11 includes any of flat portion 11 f and notch portion 11 n. InP crystal substrate 11 contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of first flat region 11 fr extending over width WR from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and first notch region 11 nr extending over width WR from notch portion 1 in to a position at a distance of 2 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface, InP crystal substrate 11 has average residual strain not less than 5×10⁶ and not more than 5×10⁻⁵. Since InP crystal substrate 11 in the present embodiment has average residual strain within a prescribed range in any of first flat region 11 fr and first notch region 11 nr, it is low in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

“Being perpendicular to the curve indicating the notch portion in the main surface” in the InP crystal substrate in the present embodiment means being perpendicular to a tangential line at each point on the curve indicating the notch portion in the main surface. The “curve” here means a line not being straight at least in part and may include a straight line in part. The crack defect ratio is varied by a diameter of the InP crystal substrate, a type (S atoms, Sn atoms, or Fe atoms) or a concentration of contained atoms, or a difference in manufacturing of a substrate or growth of an epitaxial layer, and being low in crack defect ratio means a relatively low crack defect ratio so long as a diameter of the InP crystal substrate, a type (S atoms, Sn atoms, or Fe atoms) or a concentration of contained atoms, and manufacturing of the substrate or growth of an epitaxial layer are identical.

Since the diameter not smaller than 100 mm and not greater than 205 mm, the thickness not smaller than 300 μm and not greater than 800 μm, S atoms at the concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at the concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at the concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³, of InP crystal substrate 11 in the present embodiment are the same as the diameter not smaller than 100 mm and not greater than 205 mm, the thickness not smaller than 300 μm and not greater than 800 μm, S atoms at the concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at the concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at the concentration not lower than 5.0×10¹⁸ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³, of InP crystal substrate 11 in Embodiment I-1, respectively, description will not be repeated. Since average residual strain in any of the first flat region and the first notch region of InP crystal substrate 11 is varied by a concentration of contained S atoms, Sn atoms, and Fe atoms, the crack defect ratio can be lowered by adjusting, at a prescribed concentration of S atoms, Sn atoms, or Fe atoms, average residual strain in any of the first flat region and the first notch region to be within a prescribed range.

From a point of view of lowering in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate, InP crystal substrate 11 in the present embodiment has average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of first flat region 11 fr extending over width WR from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and first notch region 11 nr extending over width WR from notch portion 11 n to a position at a distance of 2 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface.

From a point of view of further lowering in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate, InP crystal substrate 11 in the present embodiment preferably has average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of second flat region 11 fr extending over width WR from flat portion 11 f to a position at a distance of 1 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and second notch region 11 nr extending over width WR from notch portion 11 n to a position at a distance of 1 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface.

The second flat region and the second notch region are partial regions closer to flat portion 11 f and notch portion 11 n in the first flat region and the first notch region, respectively. The second flat region and the second notch region which are parts of the first flat region and the first notch region on the outer circumferential side may be greater in average residual strain than the first flat region and the first notch region, respectively. Since crack originates from the outer circumferential portion, a value of average residual strain in the second flat region more affects the crack defect ratio. Therefore, the InP crystal substrate having the average residual strain within the range above also in the second flat region and the second notch region which may be great in average residual strain is lower in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

FIG. 4 is an enlarged schematic cross-sectional view showing an exemplary portion of measurement of average residual strain in InP crystal substrate 11 in the present embodiment. Referring to FIG. 4, in specific regions each having a prescribed size and distributed evenly at prescribed pitches over the entire mirror-finished main surface in first or second flat region 11 fr or first or second notch region 11 nr, polarized light PL having a wavelength of 1.3 μm is transmitted perpendicularly to the main surface. Intensity of transmitted light obtained by synchronized rotation of a polarizer and an analyzer arranged in front and rear of a sample is collected as a function of a polarization angle ϕ. Phase retardation of birefringence and an orientation of a principal axis can be found based on polarization angle 4 and intensity of transmitted light to find an in-plane strain component. Absolute values at points, of differences in elongation and contraction strain in a direction of radius and a direction of a tangential line in a cylindrical coordinate system are averaged and calculated as average residual strain.

Since length LR (an OF length and an IF length) of flat portion 11 f and the shape and the direction of the central cut of the notch of notch portion 11 n of InP crystal substrate 11 in the present embodiment are the same as length LR (an OF length and an IF length) of flat portion 11 f and the shape and the direction of the central cut of the notch of notch portion 11 n of InP crystal substrate 11 in Embodiment I-1, respectively, description will not be repeated.

Embodiment I-3

Referring to FIGS. 1A, 1B, 2A, and 2B, InP crystal substrate 11 in the present embodiment includes a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm. A part of the outer edge of InP crystal substrate 11 includes any of flat portion 11 f and notch portion 11 n. InP crystal substrate 11 contains any of S atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³. In any of first flat region 11 fr extending over width WR from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and first notch region 11 nr extending over width WR from notch portion 11 n to a position at a distance of 2 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface, when InP crystal substrate 11 contains S atoms, InP crystal substrate 11 preferably has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵, and when InP crystal substrate 11 contains any of Sn atoms and Fe atoms, InP crystal substrate 11 preferably has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵. Since InP crystal substrate 11 in the present embodiment has an average dislocation density and average residual strain within respective prescribed ranges in any of first flat region 11 fr and first notch region 11 nr, it is lower in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

“Being perpendicular to the curve indicating the notch portion in the main surface” in the InP crystal substrate in the present embodiment means being perpendicular to a tangential line at each point on the curve indicating the notch portion in the main surface. The “curve” here means a line not being straight at least in part and may include a straight line in part. The crack defect ratio is varied by a diameter of the InP crystal substrate, a type (S atoms, Sn atoms, or Fe atoms) or a concentration of contained atoms, or a difference in manufacturing of a substrate or growth of an epitaxial layer, and being lower in crack defect ratio means a relatively lower crack defect ratio so long as a diameter of the InP crystal substrate, a type (S atoms, Sn atoms, or Fe atoms) or a concentration of contained atoms, and manufacturing of the substrate or growth of an epitaxial layer are identical.

Since the diameter not smaller than 100 mm and not greater than 205 mm, the thickness not smaller than 300 μm and not greater than 800 μm, S atoms at the concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at the concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at the concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³, of InP crystal substrate 11 in the present embodiment are the same as the diameter not smaller than 100 mm and not greater than 205 mm, the thickness not smaller than 300 μm and not greater than 800 μm, S atoms at the concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, Sn atoms at the concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and Fe atoms at the concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³, of InP crystal substrate 11 in Embodiments I-1 and I-2, respectively, description will not be repeated. Since the average dislocation density and the average residual strain in any of the first flat region and the first notch region of InP crystal substrate 11 are varied by the concentration of contained S atoms, Sn atoms, and Fe atoms, the crack defect ratio can be lowered by adjusting, at a prescribed concentration of S atoms, Sn atoms, or Fe atoms, the average dislocation density and the average residual strain in any of the first flat region and the first notch region to be within prescribed ranges.

From a point of view of lowering in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate in InP crystal substrate 11 in the present embodiment, in any of first flat region 11 ft extending over width WR from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and first notch region 11 nr extending over width WR from notch portion 11 n to a position at a distance of 2 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface, when InP crystal substrate 11 contains S atoms, it preferably has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵, and when InP crystal substrate 11 contains any of Sn atoms and Fe atoms, it preferably has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵. The average dislocation density in InP crystal substrate 11 is measured as in Embodiment I-1 and the average residual strain in InP crystal substrate 11 is measured as in Embodiment I-2.

From a point of view of further lowering in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate in InP crystal substrate 11 in the present embodiment, in any of second flat region 11 fr extending over width WR from flat portion 11 f to a position at a distance of 1 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface and second notch region 11 nr extending over width WR from notch portion 11 n to a position at a distance of 1 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface, when InP crystal substrate 11 contains S atoms, it more preferably has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵, and when InP crystal substrate 11 contains any of Sn atoms and Fe atoms, it more preferably has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻² and average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵.

The second flat region and the second notch region are partial regions closer to flat portion 11 f and notch portion 11 n in the first flat region and the first notch region, respectively. The second flat region and the second notch region which are parts of the first flat region and the first notch region on the outer circumferential side may be higher in average dislocation density and average residual strain than the first flat region and the first notch region, respectively. Since crack originates from the outer circumferential portion, values of the average dislocation density and the average residual strain in the second flat region more affects the crack defect ratio. Therefore, the InP crystal substrate having the average dislocation density and the average residual strain within the ranges above also in the second flat region and the second notch region which may be high in average dislocation density and average residual strain is lower in crack defect ratio in manufacturing of the substrate and in growth of an epitaxial layer on the substrate.

Since length LR (an OF length and an IF length) of flat portion 11 f and a size of a cut portion in notch portion 11 n in InP crystal substrate 11 in the present embodiment are the same as length LR (an OF length and an IF length) of flat portion 11 f and a size of a cut portion in notch portion 11 n in InP crystal substrate 11 in Embodiments I-1 and I-2, respectively, description will not be repeated.

<Method of Manufacturing InP Crystal Substrate>

FIGS. 5A, 5B, 6A, 6B, 7A, and 7B are schematic cross-sectional views showing an exemplary method of manufacturing InP crystal substrate 11 in Embodiments I-1 to I-3. FIGS. 5A, 6A, and 7A are vertical schematic cross-sectional views of the inside of a manufacturing apparatus and FIGS. 5B, 6B, and 7B are horizontal schematic cross-sectional views of a heat-insulating material and the inside of a crucible. FIG. 8 is a schematic plan view showing another exemplary method of manufacturing InP crystal substrate 11 in Embodiments I-1 to I-3.

Referring to FIGS. 5A, 5B, 6A, 6B, 7A, 7B, and 8, a general method of manufacturing InP crystal substrate 11 includes growing crystals by a vertical boat method such as the vertical Bridgman (VB) method and the vertical gradient freeze (VGF) method by using a crystal growth apparatus 100 including a crucible 101, a crucible base 102, and a heater 103 arranged in a pressure vessel 105. Initially, an InP seed crystal 10 s and an InP source material 9 are arranged in crucible 101. Then, by adjusting a temperature of heater 103 and vertically moving crucible 101, InP source material 9 is molten. An InP crystalline body 10 is grown by solidifying molten InP source material 9 from a side of InP seed crystal 10 s (FIGS. 5A, 5B, 6A, and 6B). Then, InP crystalline body 10 is cooled. Then, cooled InP crystalline body 10 is taken out of crucible 101. Then, InP crystal substrate 11 is cut from taken InP crystalline body 10 (FIGS. 7A and 7B). Then, by grinding and/or polishing an outer edge (outer circumference) of cut InP crystal substrate 11, any of flat portion 11 f and notch portion 11 n is formed in a part of the outer edge (outer circumference) of InP crystal substrate 11 (FIG. 8). A main surface of InP crystal substrate 11 having any of flat portion 11 f and notch portion 11 n formed in a part of the outer edge (outer circumference) is mirror polished.

Embodiment II-1

Referring to FIGS. 5A, 5B, 6A, and 6B, in the method of manufacturing InP crystal substrate 11 in the present embodiment, a heat-insulating material 104 including a portion high in insulation and a portion low in insulation is arranged on an outer side of an outer circumference of crucible 101 in growing and cooling InP crystalline body 10 or in cooling InP crystalline body 10 (that is, at least in cooling of InP crystalline body 10) in the general manufacturing method. In InP crystalline body 10, a temperature difference between a portion to subsequently be any of flat portion 11 f and notch portion 11 n of InP crystal substrate 11 (such a portion also being referred to as an intended flat portion 10 f and an intended notch portion 10 n of InP crystalline body 10, to be understood similarly below) and a portion to be an inner side of InP crystal substrate 11 (such a portion also being referred to as an intended inner substrate portion of InP crystalline body 10, to be understood similarly below) is thus suppressed, so that a crystal defect such as dislocation and strain in first and second flat regions 11 fr and first and second notch regions 11 nr in InP crystal substrate 11 are lessened and an average dislocation density and average residual strain in first and second flat regions 11 fr and first and second notch regions 11 nr can be adjusted to be within prescribed ranges.

Arrangement of heat-insulating material 104 is not particularly restricted. From the points of view above, however, the portion high in insulation of heat-insulating material 104 is preferably arranged on the outer side of the outer edge (outer circumference) of any of intended flat portion 10 f and intended notch portion 10 n of InP crystalline body 10 (that is, a portion to be any of flat portion 11 f and notch portion 11 n of InP crystal substrate 11). For example, a portion in heat-insulating material 104 on the outer side of the outer edge (outer circumference) of any of intended flat portion 10 f and intended notch portion 10 n of InP crystalline body 10 is preferably larger in thickness or made of a material higher in insulation than a portion other than that.

Heat-insulating material 104 may be an integrated material as shown in FIGS. 5A and 5B or an assembly of a plurality of components as shown in FIGS. 6A and 6B. When heat-insulating material 104 is an integrated material, the portion of heat-insulating material 104 located on the outer side of the outer edge (outer circumference) of any of intended flat portion 10 f and intended notch portion 10 n of InP crystalline body 10 is preferably greater in thickness (FIGS. 5A and 5B) or made of a material higher in insulation than a portion other than that. When heat-insulating material 104 is an assembly of a plurality of components, the component of heat-insulating material 104 located on the outer side of the outer edge (outer circumference) of any of intended flat portion 10 f and intended notch portion 10 n of InP crystalline body 10 is preferably greater in thickness (FIGS. 6A and 6B) or made of a material higher in insulation than a portion other than that.

Though a material for heat-insulating material 104 is not particularly restricted so long as it achieves a heat insulating effect, a carbon material, ceramics, silicon nitride (SiN), silicon carbide (SiC), quartz, and a cylindrical container filled with indium phosphide (InP) are preferred.

Embodiment II-2

Referring to FIGS. 7A and 7B, in the method of manufacturing InP crystal substrate 11 in the present embodiment, in cutting InP crystal substrate 11 from taken InP crystalline body 10 in the general manufacturing method, the InP crystal substrate is cut such that a portion of InP crystal substrate 11 where any of flat portion 11 f and notch portion 11 n is to be formed is located in the inside as being more distant from the outer edge (outer circumference) of InP crystalline body 10 than other portions. Thus, a temperature difference between a portion of the InP crystal substrate where any of flat portion 11 f and the notch portion is to be formed and a portion on the inner side in InP crystal substrate 11 can be suppressed so that a crystal defect such as dislocation and strain in first and second flat regions 11 fr and first and second notch regions 11 nr of InP crystal substrate 11 can be lessened and an average dislocation density and average residual strain can be adjusted to be within prescribed ranges.

Embodiment II-3

Referring to FIG. 8, in the method of manufacturing InP crystal substrate 11 in the present embodiment, in forming any of flat portion 11 f and notch portion 11 n in a part of the outer edge (outer circumference) of InP crystal substrate 11 by grinding and/or polishing the outer edge (outer circumference) of cut InP crystal substrate 11 in the general manufacturing method, a temperature is adjusted to remove heat generated in formation of any of flat portion 11 f and notch portion 11 n. Thus, a temperature difference between a portion of the InP crystal substrate where any of flat portion 11 f and notch portion 11 n is formed and a portion on the inner side of InP crystal substrate 11 can be suppressed so that a crystal defect such as dislocation and strain in first and second flat regions 11 fr and first and second notch regions 11 nr of InP crystal substrate 11 can be lessened and an average dislocation density and average residual strain in first and second flat regions 11 fr and first and second notch regions 11 nr can be adjusted to be within prescribed ranges.

The method of grinding and/or polishing the outer edge (outer circumference) of cut InP crystal substrate 11 is not particularly restricted, and a grindstone 201 as shown, for example, in FIG. 8 can be employed. The method of adjusting a temperature for removing heat generated in formation of any of flat portion 11 f and notch portion 11 n is not particularly restricted, and a method of increasing an amount of cooling water 202 w injected from a cooling water container 202 u and/or a method of lowering a temperature of cooling water 202 w only when any of flat portion 11 f and notch portion 11 n is formed in a part of the outer edge (outer circumference) of InP crystal substrate 11 are/is available.

In the method of manufacturing InP crystal substrate 11 in Embodiments II-1 to II-3, by combining the method of manufacturing InP crystal substrate 11 in Embodiment II-1 with the method of manufacturing InP crystal substrate 11 in Embodiment II-3 or by combining the method of manufacturing InP crystal substrate 11 in Embodiment II-2 with the method of manufacturing InP crystal substrate 11 in Embodiment II-3, a temperature difference between a portion of the InP crystal substrate where any of flat portion 11 f and notch portion 11 n is formed and a portion on the inner side of InP crystal substrate 11 can further be suppressed and a crystal defect such as dislocation and strain in first and second flat regions 11 fr and first and second notch regions 11 nr of InP crystal substrate 11 can further be lessened, so that an average dislocation density and average residual strain in first and second flat regions 11 fr and first and second notch regions can be adjusted to be within prescribed ranges.

EXAMPLES Experimental Example 1

InP crystal substrate 11 including a main surface having a plane orientation of (100), including two flat portions 11 f of orientation flat (OF) having a length of 32.5 mm and identification flat (IF) having a length of 18 mm in an outer edge, and having a diameter of four inches (101.6 mm), a thickness of 650 μm, and an S atomic concentration of 2.0×10¹⁸ cm⁻³ was fabricated by using a crystal growth apparatus shown in FIGS. 5A and 5B. An average dislocation density and average residual strain in first flat region 11 fr (a region extending over a width from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface) were measured and a crack defect ratio in polishing of the InP crystal substrate and in growth of an epitaxial layer having a thickness of 1 μm on the InP crystal substrate after polishing of the InP crystal substrate was calculated. Specific description is as follows.

1. Growth of InP Crystalline Body

InP crystalline body 10 was grown by the VB method shown in FIGS. 5A and 5B. In such crystal growth, heat-insulating material 104 as an integrated material was arranged around crucible 101 during growth of crystals by melting and solidification of a source material and cooling of grown crystals. Solid carbon was employed for heat-insulating material 104, and the heat-insulating material was large in thickness in a portion located on the outer side of intended flat portion 10 f of InP crystalline body 10 and small in thickness in a portion located on the outer side of a portion other than intended flat portion 10 f of InP crystalline body 10. Thus, the average dislocation density and the average residual strain in obtained InP crystal substrate 11 could be adjusted to be within prescribed ranges. InP crystalline body 10 which had undergone crystal growth and cooling was taken out of the crucible.

2. Fabrication of InP Crystal Substrate

InP crystal substrate 11 was cut from taken InP crystalline body 10. By grinding and polishing the outer edge (outer circumference) of cut InP crystal substrate 11, two flat portions 11 f of OF having a length of 32.5 mm and IF having a length of 18 mm were formed in a part of the outer edge (outer circumference) of InP crystal substrate 11. An amount of cooling water 202 w injected from cooling water container 202 u was increased only while flat portion 11 f was formed. Thus, the average dislocation density and the average residual strain in the first flat region of obtained InP crystal substrate 11 could be adjusted to be within prescribed ranges.

3. Evaluation of Average Dislocation Density

The main surface of obtained InP crystal substrate 11 was mirror-polished, and thereafter the InP crystal substrate was immersed for two minutes at 25° C. in a mixture solution of 85 mass % of phosphoric acid and 47 mass % of hydrobromic acid at a volume ratio of 2:1. Thereafter, the average dislocation density was measured by using a microscope, as an average per unit area of etch pits (etch pit average density) produced in first flat region 11 fr (a region extending over a width from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface) in the main surface. In Experimental Examples including the present Experimental Example, the average dislocation density in first or second flat region 11 fr or first or second notch region 11 nr in the main surface is the same as the average dislocation density in first flat region 11 frc or first notch region 11 nrc in the central portion exposed by grinding.

4. Evaluation of Average Residual Strain

After the main surface of obtained InP crystal substrate 11 was mirror-polished, incident light having a beam diameter of 100 μm and a wavelength of 1.3 μm was transmitted perpendicularly to the main surface, to points arranged at pitches of 200 μm over the entire main surface in mirror-polished first flat region 11 fr (a region extending over a width from flat portion 11 f to a position at a distance of 2 mm in the direction perpendicular to the straight line indicating flat portion 11 f in the main surface). Phase retardation of birefringence and an orientation of a principal axis of a sample were calculated based on relation between obtained intensity of transmitted light and a polarization angle. Absolute values of differences in elongation and contraction strain in a direction of radius and a direction of a tangential line at those points in a cylindrical coordinate system were calculated, and an average of the absolute values of the differences in elongation and contraction strain at those points was calculated as the average residual strain.

5. Evaluation of Crack Defect Ratio

The crack defect ratio refers to a percentage of samples where crack occurred with respect to the total number of samples in manufacturing of a substrate and in growth of an epitaxial layer below.

(1) In Manufacturing of Substrate

A crack defect ratio of obtained InP crystal substrate 11 was calculated at the time when the InP crystal substrate was subjected to double-sided polishing as primary polishing for 90 minutes under such conditions as the number of rotations of an upper surface of 15 rpm, the number of rotations of a lower surface of 35 rpm, carrier revolution of 10 rpm, and carrier rotation of 5 rpm with an abrasive containing colloidal silica being dropped at 300 cm⁻³/minute and with the use of a polishing cloth of a nonwoven type and subjected to single-sided polishing as finishing polishing for 15 minutes under such conditions as the number of revolutions of the upper surface of 60 rpm and the number of revolutions of the lower surface of 60 rpm with an abrasive not containing colloidal silica being dropped at 150 cm⁻³/minute and with the use of a polishing cloth of a suede type.

(2) In Growth of Epitaxial Layer

A crack defect ratio of obtained InP crystal substrate 11 was calculated after it was subjected to primary polishing and finishing polishing and thereafter an InP layer having a thickness of 1 μm was grown as an epitaxial layer on the main surface subjected to finishing polishing by metal-organic chemical vapor deposition (MOCVD) under such conditions as a temperature of a crystal growth atmosphere of 600° C., a pressure of the crystal growth atmosphere of 50 Torr, and a V/III ratio (representing a ratio of a molarity of a V group element to a molarity of a III group element, to be understood similarly below) of 100.

Table 1 summarizes a crack defect ratio in manufacturing of the substrate and Table 2 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 10 cm⁻² to 500 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 2 cm⁻² and 1500 cm⁻² with Examples where the average residual strain in the first flat region was from 5.0×10⁻² to 5.0×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 3.0×10⁻⁶ and 1.0×10⁻⁴ in the present Experimental Example (Experimental Example 1).

TABLE 1 Crack Defect Ratio (%) in Manufacturing of Substrate [S Atomic Concentration: 2.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 2 10 60 200 500 1500 Average 3.0 × 10⁻⁶ 3.5 2.5 2.2 2.6 2.2 3.6 Residual 5.0 × 10⁻⁶ 2.2 1.5 1.3 1.4 1.2 2.5 Strain 1.5 × 10⁻⁵ 2.3 1.0 1.5 1.5 1.4 2.4 5.0 × 10⁻⁵ 2.5 1.4 1.5 1.3 1.2 2.2 1.0 × 10⁻⁴ 3.8 2.6 2.4 2.6 2.3 4.0

TABLE 2 Crack Defect Ratio (%) in Epitaxial Layer Growth [S Atomic Concentration: 2.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 2 10 60 200 500 1500 Average 3.0 × 10⁻⁶ 2.0 1.2 1.7 1.7 1.9 2.5 Residual 5.0 × 10⁻⁶ 1.4 0.5 0.4 0.4 0.2 1.8 Strain 1.5 × 10⁻⁵ 1.6 0.6 0.5 0.2 0.6 1.8 5.0 × 10⁻⁵ 1.5 0.4 0.3 0.5 0.3 1.6 1.0 × 10⁻⁴ 2.5 1.6 1.4 1.8 1.3 2.4

Experimental Example 2

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 1 except for setting an S atomic concentration to 5.0×10¹⁸ cm⁻³. Table 3 summarizes a crack defect ratio in manufacturing of the substrate and Table 4 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 15 cm⁻² to 480 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 1 cm⁻² and 2000 cm⁻² with Examples where the average residual strain in the first flat region was from 5.3×10⁻⁶ to 4.5×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 2.2×10⁻⁶ and 2.0×10⁻⁴ in the present Experimental Example (Experimental Example 2).

TABLE 3 Crack Defect Ratio (%) in Manufacturing of Substrate [S Atomic Concentration: 5.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 1 15 100 300 480 2000 Average 2.2 × 10⁻⁶ 3.6 2.5 2.8 2.2 2.6 3.8 Residual 5.3 × 10⁻⁶ 2.4 1.2 1.4 1.3 1.2 2.4 Strain 1.0 × 10⁻⁵ 2.4 1.5 1.0 1.2 1.5 2.6 4.5 × 10⁻⁵ 2.5 1.1 1.3 1.1 1.4 2.6 2.0 × 10⁻⁴ 3.3 2.6 2.8 2.2 2.4 3.8

TABLE 4 Crack Defect Ratio (%) in Epitaxial Layer Growth [S Atomic Concentration: 5.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 1 15 100 300 480 2000 Average 2.2 × 10⁻⁶ 2.3 1.5 1.5 1.4 1.6 2.2 Residual 5.3 × 10⁻⁶ 1.5 0.7 0.8 0.4 0.6 1.6 Strain 1.0 × 10⁻⁵ 1.2 0.4 0.6 0.5 0.8 1.6 4.5 × 10⁻⁵ 1.6 0.6 0.6 0.3 0.5 1.8 2.0 × 10⁻⁴ 2.8 1.3 1.6 1.8 1.7 2.7

Experimental Example 3

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 1 except for setting an S atomic concentration to 8.0×10¹⁸ cm⁻³. Table 5 summarizes a crack defect ratio in manufacturing of the substrate and Table 6 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 12 cm⁻² to 460 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 3 cm⁻² and 1000 cm⁻² with Examples where the average residual strain in the first flat region was from 5.1×10⁻⁶ to 4.8×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 1.0×10⁻⁶ and 1.5×10⁻⁴ in the present Experimental Example (Experimental Example 3).

TABLE 5 Crack Defect Ratio (%) in Manufacturing of Substrate [S Atomic Concentration: 8.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 3 12 120 250 460 1000 Average 1.0 × 10⁻⁶ 3.5 2.4 2.5 2.5 2.4 3.8 Residual 5.1 × 10⁻⁶ 2.2 1.2 1.2 1.1 1.4 2.5 Strain 2.5 × 10⁻⁵ 2.8 1.2 1.5 1.3 1.0 2.6 4.8 × 10⁻⁵ 2.6 1.3 1.0 1.1 1.2 2.4 1.5 × 10⁻⁴ 3.0 2.4 2.6 2.8 2.2 3.5

TABLE 6 Crack Defect Ratio (%) in Epitaxial Layer Growth [S Atomic Concentration: 8.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 3 12 120 250 460 1000 Average 1.0 × 10⁻⁶ 2.2 1.6 1.7 1.6 1.9 2.8 Residual 5.1 × 10⁻⁶ 1.6 0.4 0.4 0.6 0.6 1.5 Strain 2.5 × 10⁻⁵ 1.8 0.6 0.6 0.8 0.5 1.9 4.8 × 10⁻⁵ 1.7 0.4 0.6 0.5 0.4 1.6 1.5 × 10⁻⁴ 2.6 1.6 1.4 1.7 1.8 2.4

Experimental Example 4

InP crystal substrate 11 was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 1 except for setting an Sn atomic concentration to 1.0×10¹⁸ cm⁻³ instead of the S atomic concentration of 2.0×10¹⁸ cm⁻³. Table 7 summarizes a crack defect ratio in manufacturing of the substrate and Table 8 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 500 cm⁻² to 5000 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 200 cm⁻² and 8500 cm⁻² with Examples where the average residual strain in the first flat region was from 5.0×10⁻⁶ to 4.7×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 3.0×10⁻⁶ and 1.2×10⁻⁴ in the present Experimental Example (Experimental Example 4).

TABLE 7 Crack Defect Ratio (%) in Manufacturing of Substrate [Sn Atomic Concentration: 1.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 200 500 2200 3500 5000 8500 Average 3.0 × 10⁻⁶ 4.4 3.3 3.2 3.4 3.2 4.3 Residual 5.0 × 10⁻⁶ 3.2 1.8 1.7 1.6 2.3 3.5 Strain 1.5 × 10⁻⁵ 3.3 1.7 2.0 2.4 1.7 3.6 4.7 × 10⁻⁵ 3.4 1.9 1.9 1.5 2.3 3.2 1.2 × 10⁻⁴ 4.2 3.3 3.4 3.6 3.6 4.0

TABLE 8 Crack Defect Ratio (%) in Epitaxial Layer Growth [Sn Atomic Concentration: 1.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 200 500 2200 3500 5000 8500 Average 3.0 × 10⁻⁶ 2.2 1.6 1.4 1.6 1.8 2.8 Residual 5.0 × 10⁻⁶ 1.6 0.6 0.3 0.7 0.3 1.6 Strain 1.5 × 10⁻⁵ 1.8 0.5 0.5 0.3 0.5 1.9 4.7 × 10⁻⁵ 1.6 0.6 0.5 0.4 0.3 1.5 1.2 × 10⁻⁴ 2.6 1.5 1.8 1.6 1.4 2.5

Experimental Example 5

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 4 except for setting an Sn atomic concentration to 3.0×10¹ cm⁻³. Table 9 summarizes a crack defect ratio in manufacturing of the substrate and Table 10 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 550 cm⁻² to 4800 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 100 cm⁻² and 12000 cm⁻² with Examples where the average residual strain in the first flat region was from 5.1×10⁻⁶ to 4.8×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 2.5×10⁻⁶ and 2.0×10⁻⁴ in the present Experimental Example (Experimental Example 5).

TABLE 9 Crack Defect Ratio (%) in Manufacturing of Substrate [Sn Atomic Concentration: 3.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 100 550 3000 3500 4800 12000 Average 2.5 × 10⁻⁶ 4.2 3.2 3.6 3.2 3.4 4.6 Residual 5.1 × 10⁻⁶ 3.5 1.6 2.2 1.7 1.5 3.8 Strain 1.0 × 10⁻⁵ 3.2 1.5 2.2 1.6 1.7 3.6 4.8 × 10⁻⁵ 3.4 1.7 2.0 1.8 2.0 3.3 2.0 × 10⁻⁴ 4.6 3.5 3.2 3.5 3.6 4.7

TABLE 10 Crack Defect Ratio (%) in Epitaxial Layer Growth [Sn Atomic Concentration: 3.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 100 550 3000 3500 4800 12000 Average 2.5 × 10⁻⁶ 2.9 1.5 1.7 1.7 1.8 2.6 Residual 5.1 × 10⁻⁶ 1.5 0.6 0.5 0.8 0.6 1.5 Strain 1.0 × 10⁻⁵ 1.9 0.6 0.6 0.4 0.4 1.9 4.8 × 10⁻⁵ 1.4 0.3 0.4 0.9 0.5 1.6 2.0 × 10⁻⁴ 2.5 1.5 1.8 1.6 1.4 2.7

Experimental Example 6

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 4 except for setting an Sn atomic concentration to 4.0×10¹⁸ cm⁻³. Table 11 summarizes a crack defect ratio in manufacturing of the substrate and Table 12 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 510 cm⁻² to 4700 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 10 cm⁻² and 7500 cm⁻² with Examples where the average residual strain in the first flat region was from 5.5×10⁻⁶ to 5.0×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 4.0×10⁻⁶ and 1.5×10⁻⁴ in the present Experimental Example (Experimental Example 6).

TABLE 11 Crack Defect Ratio (%) in Manufacturing of Substrate [Sn Atomic Concentration: 4.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 10 510 1200 2800 4700 7500 Average 4.0 × 10⁻⁶ 4.7 3.4 3.7 3.2 3.8 5.0 Residual 5.5 × 10⁻⁶ 3.5 2.0 1.9 1.6 2.3 3.5 Strain 2.0 × 10⁻⁵ 3.4 1.8 2.3 2.2 1.9 3.6 5.0 × 10⁻⁵ 3.3 2.3 1.8 1.6 1.8 4.0 1.5 × 10⁻⁴ 4.2 3.5 3.0 3.2 3.5 5.2

TABLE 12 Crack Defect Ratio (%) in Epitaxial Layer Growth [Sn Atomic Concentration: 4.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 10 510 1200 2800 4700 7500 Average 4.0 × 10⁻⁶ 2.5 1.5 1.3 1.6 1.5 2.4 Residual 5.5 × 10⁻⁶ 1.6 0.6 0.6 0.6 0.3 1.6 Strain 2.0 × 10⁻⁵ 1.8 0.8 0.2 0.5 0.5 1.5 5.0 × 10⁻⁵ 1.8 0.4 0.3 0.9 0.6 1.8 1.5 × 10⁻⁴ 2.6 1.5 1.4 1.6 1.5 2.8

Experimental Example 7

InP crystal substrate 11 was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 1 except for setting an Fe atomic concentration to 1.0×10¹⁶ cm⁻³ instead of the S atomic concentration of 2.0×10¹⁸ cm⁻³. Table 13 summarizes a crack defect ratio in manufacturing of the substrate and Table 14 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 500 cm⁻² to 5000 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 200 cm⁻² and 8500 cm⁻² with Examples where the average residual strain in the first flat region was from 5.5×10⁻⁶ to 5.0×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 2.0×10⁻⁶ and 2.0×10⁻⁴ in the present Experimental Example (Experimental Example 7).

TABLE 13 Crack Defect Ratio (%) in Manufacturing of Substrate [Fe Atomic Concentration: 1.0 × 10¹⁶ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 200 500 2200 3500 5000 8500 Average 2.0 × 10⁻⁶ 4.7 2.5 2.6 2.8 2.6 4.6 Residual 5.5 × 10⁻⁶ 2.8 1.2 0.5 0.7 1.0 2.5 Strain 1.0 × 10⁻⁵ 2.9 0.7 1.2 0.6 0.6 2.8 5.0 × 10⁻⁵ 2.6 1.6 1.5 1.0 1.2 2.6 2.0 × 10⁻⁴ 3.9 2.8 2.6 2.8 2.7 4.2

TABLE 14 Crack Defect Ratio (%) in Epitaxial Layer Growth [Fe Atomic Concentration: 1.0 × 10¹⁶ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 200 500 2200 3500 5000 8500 Average 2.0 × 10⁻⁶ 2.5 1.5 1.6 1.5 1.8 2.2 Residual 5.5 × 10⁻⁶ 1.6 0.6 0.8 0.4 0.6 1.6 Strain 1.0 × 10⁻⁵ 1.8 0.7 0.5 0.6 0.8 1.5 5.0 × 10⁻⁵ 1.5 0.6 0.4 0.5 0.7 1.4 2.0 × 10⁻⁴ 2.8 1.6 1.5 1.6 1.7 2.4

Experimental Example 8

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 m which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 7 except for setting an Fe atomic concentration to 2.0×10¹⁶ cm⁻³. Table 15 summarizes a crack defect ratio in manufacturing of the substrate and Table 16 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 550 cm⁻² to 4500 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 100 cm⁻² and 15000 cm⁻² with Examples where the average residual strain in the first flat region was from 5.0×10⁻⁶ to 4.9×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 3.0×10⁻⁶ and 1.0×10⁻⁴ in the present Experimental Example (Experimental Example 8).

TABLE 15 Crack Defect Ratio (%) in Manufacturing of Substrate [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 100 550 3000 3800 4500 15000 Average 3.0 × 10⁻⁶ 4.2 2.6 2.5 2.7 2.4 3.6 Residual 5.0 × 10⁻⁶ 2.6 0.7 0.8 0.6 0.6 2.6 Strain 8.0 × 10⁻⁶ 2.6 1.0 0.6 0.6 1.0 2.8 4.9 × 10⁻⁵ 2.8 1.2 1.0 1.2 0.7 2.7 1.0 × 10⁻⁴ 4.5 2.5 2.4 2.8 2.4 3.8

TABLE 16 Crack Defect Ratio (%) in Epitaxial Layer Growth [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 100 550 3000 3800 4500 15000 Average 3.0 × 10⁻⁶ 2.5 1.8 1.6 1.7 1.5 2.8 Residual 5.0 × 10⁻⁶ 1.6 0.6 0.5 0.3 0.5 1.6 Strain 8.0 × 10⁻⁶ 1.8 0.4 0.8 0.8 0.8 1.4 4.9 × 10⁻⁵ 1.5 0.4 0.5 0.7 0.4 1.4 1.0 × 10⁻⁴ 2.4 1.7 1.5 1.8 1.6 2.6

Experimental Example 9

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the first flat region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 7 except for setting an Fe atomic concentration to 5.0×10¹⁶ cm⁻³. Table 17 summarizes a crack defect ratio in manufacturing of the substrate and Table 18 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first flat region was from 510 cm⁻² to 4800 cm⁻² and Comparative Examples where the average dislocation density in the first flat region was 260 cm⁻² and 7500 cm⁻² with Examples where the average residual strain in the first flat region was from 5.6×10⁻⁶ to 4.5×10⁻⁵ and Comparative Examples where the average residual strain in the first flat region was 3.5×10⁻⁶ and 1.5×10⁻⁴ in the present Experimental Example (Experimental Example 9).

TABLE 17 Crack Defect Ratio (%) in Manufacturing of Substrate [Fe Atomic Concentration: 5.0 × 10¹⁶ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 260 510 1200 3000 4800 7500 Average 3.5 × 10⁻⁶ 3.8 2.3 2.5 2.4 2.4 3.8 Residual 5.6 × 10⁻⁶ 2.4 0.8 0.8 1.0 0.5 2.8 Strain 1.5 × 10⁻⁵ 2.6 0.8 1.1 0.8 0.9 2.6 4.5 × 10⁻⁵ 2.5 0.6 0.6 1.0 0.5 2.4 1.5 × 10⁻⁴ 3.6 2.6 2.1 2.8 2.6 4.5

TABLE 18 Crack Defect Ratio (%) in Epitaxial Layer Growth [Fe Atomic Concentration: 5.0 × 10¹⁶ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [First Flat Region] 260 510 1200 3000 4800 7500 Average 3.5 × 10⁻⁶ 2.5 1.5 1.7 1.8 1.9 2.6 Residual 5.6 × 10⁻⁶ 1.6 0.5 0.4 0.8 0.6 1.5 Strain 1.5 × 10⁻⁵ 1.8 0.5 0.7 0.3 0.4 1.3 4.5 × 10⁻⁵ 1.4 0.6 0.6 0.5 0.6 1.6 1.5 × 10⁻⁴ 3.0 1.6 1.5 1.5 1.6 2.8

Experimental Example 10

InP crystal substrate 11 including a main surface having a plane orientation of (100), including notch portion 11 n machined into a shape by cutting off a portion extending by 1.0 mm from the outer edge toward the center at an opening angle of 90° in a [010] direction when the direction of the central cut of the notch was viewed from the center of the substrate, and having a diameter of six inches (152.4 mm), a thickness of 650 μm, and an Fe atomic concentration of 2.0×10¹⁶ cm⁻³ was fabricated by using a crystal growth apparatus shown in FIG. 6. An average dislocation density and average residual strain in first notch region 11 nr (a region extending over a width from notch portion 11 n to a position at a distance of 2 mm in the direction perpendicular to the curve indicating notch portion 11 n in the main surface) were measured and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated. Specific description is as follows.

1. Growth of InP Crystalline Body

InP crystalline body 10 was grown by the VB method shown in FIG. 6. Heat-insulating material 104 as an assembly of a plurality of components was arranged around crucible 101 during growth of crystals by melting and solidification of a source material and cooling of growth crystals. Heat-insulating material 104 was composed of solid carbon covered with pyrolytic boron nitride (pBN), and a component thereof large in thickness was located on the outer side of intended notch portion 10 n of InP crystalline body 10 and a component thereof small in thickness was located on the outer side of a portion other than intended notch portion 10 n of InP crystalline body 10. The average dislocation density and the average residual strain in obtained InP crystal substrate 11 could thus be adjusted to be within prescribed ranges. InP crystalline body 10 which had undergone crystal growth and cooling was taken out of the crucible.

2. Fabrication of InP Crystal Substrate

InP crystal substrate 11 was cut from taken InP crystalline body 10. By grinding and polishing the outer edge (outer circumference) of cut InP crystal substrate 11, notch portion 11 n machined into a shape by cutting off a portion extending by 1.0 mm from the outer edge toward the center at an opening angle of 90° in a [010] direction when the direction of the central cut of the notch was viewed from the center of the substrate was provided in a part of the outer edge (outer circumference) of InP crystal substrate 11. An amount of cooling water 202 w injected from cooling water container 202 u was increased only while notch portion 11 n was provided. The average dislocation density and the average residual strain in obtained InP crystal substrate 11 could thus be adjusted to be within prescribed ranges.

The average dislocation density, the average residual strain, and the crack defect ratio of obtained InP crystal substrate 11 were evaluated as in Experimental Example 1. Table 19 summarizes a crack defect ratio in manufacturing of the substrate and Table 20 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first notch region was from 500 cm⁻² to 4900 cm⁻² and Comparative Examples where the average dislocation density in the first notch region was 250 cm⁻² and 22000 cm⁻² with Examples where the average residual strain in the first notch region was from 5.2×10⁻⁶ to 4.7×10⁻⁵ and Comparative Examples where the average residual strain in the first notch region was 2.5×10⁻⁶ and 1.5×10⁻⁴ in the present Experimental Example (Experimental Example 10).

TABLE 19 Crack Defect Ratio (%) in Manufacturing of Substrate [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 6 inches] Average Dislocation Density (cm⁻²) [First Notch Region] 250 500 2000 3000 4900 22000 Average 2.5 × 10⁻⁶ 5.4 4.3 4.5 4.5 4.9 5.3 Residual 5.2 × 10⁻⁶ 4.5 2.7 2.3 2.8 2.7 4.5 Strain 9.0 × 10⁻⁶ 4.6 2.0 2.6 2.3 2.4 4.3 4.7 × 10⁻⁵ 4.8 3.0 2.3 2.3 2.7 4.8 1.5 × 10⁻⁴ 5.9 4.8 4.4 4.3 4.4 5.0

TABLE 20 Crack Defect Ratio (%) in Epitaxial Layer Growth [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 6 inches] Average Dislocation Density (cm⁻²) [First Notch Region] 250 500 2000 3000 4900 22000 Average 2.5 × 10⁻⁶ 4.5 3.8 4.0 3.5 3.8 5.0 Residual 5.2 × 10⁻⁶ 3.6 2.5 2.4 2.5 2.6 3.6 Strain 9.0 × 10⁻⁶ 3.8 2.0 2.6 2.7 2.8 3.5 4.7 × 10⁻⁵ 3.6 2.8 2.6 2.6 2.3 3.3 1.5 × 10⁻⁴ 4.8 3.8 3.3 3.7 3.8 4.4

Experimental Example 11

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the first notch region were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 10 except for setting a diameter to eight inches (203.2 mm). Table 21 summarizes a crack defect ratio in manufacturing of the substrate and Table 22 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the first notch region was from 520 cm⁻² to 4500 cm⁻² and Comparative Examples where the average dislocation density in the first notch region was 300 cm⁻² and 19000 cm⁻² with Examples where the average residual strain in the first notch region was from 5.5×10⁻⁶ to 5.0×10⁻⁵ and Comparative Examples where the average residual strain in the first notch region was 4.0×10⁻⁶ and 1.3×10⁻⁴ in the present Experimental Example (Experimental Example 11).

TABLE 21 Crack Defect Ratio (%) in Manufacturing of Substrate [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 8 inches] Average Dislocation Density (cm⁻²) [First Notch Region] 300 520 1000 3300 4500 19000 Average 4.0 × 10⁻⁶ 6.5 5.5 5.6 5.4 5.3 6.6 Residual 5.5 × 10⁻⁶ 5.4 3.7 3.4 3.6 3.3 5.0 Strain 1.2 × 10⁻⁵ 5.6 3.8 3.6 3.8 3.4 5.5 5.0 × 10⁻⁵ 5.7 3.2 3.4 3.3 3.5 5.4 1.3 × 10⁻⁴ 6.8 5.5 5.5 5.6 5.3 7.0

TABLE 22 Crack Defect Ratio (%) in Epitaxial Layer Growth [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 8 inches] Average Dislocation Density (cm⁻²) [First Notch Region] 300 520 1000 3300 4500 19000 Average 4.0 × 10⁻⁶ 5.4 4.3 4.5 4.6 4.3 6.2 Residual 5.5 × 10⁻⁶ 4.6 3.3 3.5 3.2 3.8 4.5 Strain 1.2 × 10⁻⁵ 4.3 3.4 3.9 3.7 3.7 4.8 5.0 × 10⁻⁵ 4.7 3.5 3.4 3.6 3.4 4.3 1.3 × 10⁻⁴ 5.6 4.8 4.5 4.8 4.5 6.0

As shown in Experimental Examples 1 to 11, it can be seen that the crack defect ratio in manufacturing of the substrate and in growth of the epitaxial layer on the substrate is low in the InP crystal substrate having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm and including any of the flat portion and the notch portion in a part of the outer edge thereof when a concentration of S atoms is not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³ and when the average dislocation density is not lower than 10 cm⁻² and not higher than 500 cm⁻² or the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the first flat region and the first notch region and when a concentration of Sn atoms is not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³ or a concentration of Fe atoms is not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³ and when the average dislocation density is not lower than 500 cm⁻² and not higher than 5000 cm⁻² or the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the first flat region and the first notch region.

Furthermore, it can be seen that the crack defect ratio in manufacturing of the substrate and in growth of the epitaxial layer on the substrate is lower in the InP crystal substrate above when a concentration of S atoms is not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³ and when the average dislocation density is not lower than 10 cm⁻² and not higher than 500 cm⁻² and the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the first flat region and the first notch region and when a concentration of Sn atoms is not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³ or a concentration of Fe atoms is not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻² and when the average dislocation density is not lower than 500 cm⁻² and not higher than 5000 cm⁻² and the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the first flat region and the first notch region.

Experimental Example 12

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the second flat region (a region extending over a width from the flat portion to a position at a distance of 1 mm in the direction perpendicular to the straight line indicating the flat portion in the main surface) were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 2 except for setting a thickness of a heat-insulating material located on the outer side of the intended flat portion of the InP crystalline body to twice as large as the thickness in Experimental Example 2. Table 23 summarizes a crack defect ratio in manufacturing of the substrate and Table 24 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the second flat region was from 15 cm⁻² to 480 cm⁻² and Comparative Examples where the average dislocation density in the second flat region was 1 cm⁻² and 2000 cm⁻² with Examples where the average residual strain in the second flat region was from 5.3×10⁻⁶ to 4.5×10⁻⁵ and Comparative Examples where the average residual strain in the second flat region was 2.2×10⁻⁶ and 2.0×10⁻⁴ in the present Experimental Example (Experimental Example 12).

TABLE 23 Crack Defect Ratio (%) in Manufacturing of Substrate [S Atomic Concentration: 5.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [Second Flat Region] 1 15 100 300 480 2000 Average 2.2 × 10⁻⁶ 1.8 1.3 1.4 1.1 1.3 1.9 Residual 5.3 × 10⁻⁶ 1.2 0.6 0.7 0.6 0.6 1.2 Strain 1.0 × 10⁻⁵ 1.2 0.7 0.5 0.6 0.7 1.3 4.5 × 10⁻⁵ 1.4 0.5 0.5 0.6 0.7 1.3 2.0 × 10⁻⁴ 1.7 1.4 1.4 1.1 1.2 1.9

TABLE 24 Crack Defect Ratio (%) in Epitaxial Layer Growth [S Atomic Concentration: 5.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [Second Flat Region] 1 15 100 300 480 2000 Average 2.2 × 10⁻⁶ 1.2 0.7 0.7 0.7 0.8 1.1 Residual 5.3 × 10⁻⁶ 0.7 0.3 0.4 0.2 0.3 0.8 Strain 1.0 × 10⁻⁵ 0.5 0.2 0.3 0.2 0.4 0.8 4.5 × 10⁻⁵ 0.8 0.3 0.2 0.1 0.2 0.9 2.0 × 10⁻⁴ 1.4 0.7 0.8 0.9 0.8 1.3

Experimental Example 13

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the second flat region (a region extending over a width from the flat portion to a position at a distance of 1 mm in the direction perpendicular to the straight line indicating the flat portion in the main surface) were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 5 except for setting a thickness of a heat-insulating material located on the outer side of the intended flat portion of the InP crystalline body to twice as large as the thickness in Experimental Example 5. Table 25 summarizes a crack defect ratio in manufacturing of the substrate and Table 26 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the second flat region was from 550 cm⁻² to 4800 cm⁻² and Comparative Examples where the average dislocation density in the second flat region was 100 cm⁻² and 12000 cm⁻² with Examples where the average residual strain in the second flat region was from 5.1×10⁻⁶ to 4.8×10⁻⁵ and Comparative Examples where the average residual strain in the second flat region was 2.5×10⁻⁶ and 2.0×10⁻⁴ in the present Experimental Example (Experimental Example 13).

TABLE 25 Crack Defect Ratio (%) in Manufacturing of Substrate [Sn Atomic Concentration: 3.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [Second Flat Region] 100 550 3000 3500 4800 12000 Average 2.5 × 10⁻⁶ 2.1 1.6 1.8 1.6 1.7 2.4 Residual 5.1 × 10⁻⁶ 1.7 0.9 1.1 0.9 0.8 1.9 Strain 1.0 × 10⁻⁵ 1.6 0.8 1.0 0.8 0.8 2.0 4.8 × 10⁻⁵ 1.7 0.8 1.0 0.9 1.0 1.7 2.0 × 10⁻⁴ 2.3 1.7 1.6 1.7 1.8 2.4

TABLE 26 Crack Defect Ratio (%) in Epitaxial Layer Growth [Sn Atomic Concentration: 3.0 × 10¹⁸ cm⁻³] [Diameter: 4 inches] Average Dislocation Density (cm⁻²) [Second Flat Region] 100 550 3000 3500 4800 12000 Average 2.5 × 10⁻⁶ 1.5 0.8 0.8 0.8 0.9 1.3 Residual 5.1 × 10⁻⁶ 0.8 0.3 0.3 0.4 0.3 0.8 Strain 1.0 × 10⁻⁵ 1.0 0.3 0.4 0.1 0.3 0.9 4.8 × 10⁻⁵ 0.7 0.1 0.2 0.5 0.2 0.8 2.0 × 10⁻⁴ 1.2 0.7 0.9 0.8 0.7 1.3

Experimental Example 14

The InP crystal substrate was fabricated, the average dislocation density and the average residual strain in the second notch region (a region extending over a width from the notch portion to a position at a distance of 1 mm in the direction perpendicular to the curve indicating the notch portion in the main surface) were measured, and a crack defect ratio in polishing of the InP crystal substrate and in growth of the InP layer having a thickness of 1 μm which was the epitaxial layer on the InP crystal substrate after polishing of the InP crystal substrate was calculated as in Experimental Example 10 except for setting a thickness of a heat-insulating material located on the outer side of the intended notch portion of the InP crystalline body to twice as large as the thickness in Experimental Example 10. Table 27 summarizes a crack defect ratio in manufacturing of the substrate and Table 28 summarizes a crack defect ratio in growth of the epitaxial layer, in combinations of Examples where the average dislocation density in the second notch region was from 500 cm⁻² to 4900 cm⁻² and Comparative Examples where the average dislocation density in the second notch region was 250 cm⁻² and 22000 cm⁻² with Examples where the average residual strain in the second notch region was from 5.2×10⁻⁶ to 4.7×10⁻⁵ and Comparative Examples where the average residual strain in the second notch region was 2.5×10⁻⁶ and 1.5×10⁻⁴ in the present Experimental Example (Experimental Example 14).

TABLE 27 Crack Defect Ratio (%) in Manufacturing of Substrate [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 6 inches] Average Dislocation Density (cm⁻²) [Second Notch Region] 250 500 2000 3000 4900 22000 Average 2.5 × 10⁻⁶ 2.7 2.2 2.3 2.3 2.5 2.6 Residual 5.2 × 10⁻⁶ 2.2 1.4 1.3 1.4 1.4 2.3 Strain 9.0 × 10⁻⁶ 2.3 1.0 1.3 1.6 1.2 2.2 4.7 × 10⁻⁵ 2.5 1.5 1.2 1.7 1.4 2.4 1.5 × 10⁻⁴ 3.0 2.5 2.2 2.2 2.4 2.5

TABLE 28 Crack Defect Ratio (%) in Epitaxial Layer Growth [Fe Atomic Concentration: 2.0 × 10¹⁶ cm⁻³] [Diameter: 6 inches] Average Dislocation Density (cm⁻²) [Second Notch Region] 250 500 2000 3000 4900 22000 Average 2.5 × 10⁻⁶ 2.3 1.9 2.0 1.7 1.9 2.5 Residual 5.2 × 10⁻⁶ 1.8 1.3 1.2 1.3 1.3 1.8 Strain 9.0 × 10⁻⁶ 1.9 1.0 1.3 1.3 1.4 1.8 4.7 × 10⁻⁵ 1.9 1.4 1.3 1.4 1.6 1.7 1.5 × 10⁻⁴ 2.5 1.7 1.6 1.8 1.9 2.3

As shown in Experimental Examples 12 to 14, it can be seen that the crack defect ratio in manufacturing of the substrate and in growth of the epitaxial layer on the substrate is low in the InP crystal substrate having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm and including any of the flat portion and the notch portion in a part of the outer edge thereof when a concentration of S atoms is not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³ and when the average dislocation density is not lower than 10 cm⁻² and not higher than 500 cm⁻² or the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the second flat region and the second notch region and when a concentration of Sn atoms is not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³ or a concentration of Fe atoms is not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³ and when the average dislocation density is not lower than 500 cm⁻² and not higher than 5000 cm⁻² or the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the second flat region and the second notch region.

Furthermore, it can be seen that the crack defect ratio in manufacturing of the substrate and in growth of the epitaxial layer on the substrate is lower in the InP crystal substrate above when a concentration of S atoms is not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³ and when the average dislocation density is not lower than 10 cm⁻² and not higher than 500 cm⁻² and the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the second flat region and the second notch region and when a concentration of Sn atoms is not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³ or a concentration of Fe atoms is not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³ and when the average dislocation density is not lower than 500 cm⁻² and not higher than 5000 cm⁻² and the average residual strain is not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of the second flat region and the second notch region.

It should be understood that the embodiments and Examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims rather than the embodiments and Examples above and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

REFERENCE SIGNS LIST

9 InP source material; 10 InP crystalline body; 10 f intended flat portion; 10 n intended notch portion; 10 s InP seed crystal; 11 InP crystal substrate; 11 f flat portion; 11 fr, 11 frc first flat region, second flat region; 11 n notch portion; 11 nr, 11 nrc first notch region, second notch region; 100 crystal growth apparatus; 101 crucible; 102 crucible base; 103 heater; 104 heat-insulating material; 105 pressure vessel; 201 grindstone; 202 u cooling water container; 202 w cooling water; LR length; WR width; PL polarized light 

The invention claimed is:
 1. An indium phosphide crystal substrate including a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm, a part of an outer edge of the indium phosphide crystal substrate including any of a flat portion and a notch portion, the indium phosphide crystal substrate containing any of sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³, and the indium phosphide crystal substrate having average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of a first flat region extending over a width from the flat portion to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a first notch region extending over a width from the notch portion to a position at a distance of 2 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, wherein in any of the first flat region and the first notch region, when the indium phosphide crystal substrate contains the sulfur atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when the indium phosphide crystal substrate contains any of the tin atoms and the iron atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².
 2. An indium phosphide crystal substrate including a main surface having a diameter not smaller than 100 mm and not greater than 205 mm and a thickness not smaller than 300 μm and not greater than 800 μm, a part of an outer edge of the indium phosphide crystal substrate including any of a flat portion and a notch portion, the indium phosphide crystal substrate containing any of sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁷ cm⁻³, and the indium phosphide crystal substrate having average residual strain not less than 5×10⁻⁶ and not more than 5×10⁻⁵ in any of a second flat region extending over a width from the flat portion to a position at a distance of 1 mm in a direction perpendicular to a straight line indicating the flat portion in the main surface and a second notch region extending over a width from the notch portion to a position at a distance of 1 mm in a direction perpendicular to a curve indicating the notch portion in the main surface, wherein in any of the second flat region and the second notch region, when the indium phosphide crystal substrate contains the sulfur atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻², and when the indium phosphide crystal substrate contains any of the tin atoms and the iron atoms, the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm^(−2.)
 3. The indium phosphide crystal substrate according to claim 1, wherein the main surface has a diameter not smaller than 100 mm and not greater than 101.6 mm, the indium phosphide crystal substrate contains sulfur atoms at a concentration not lower than 5.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻².
 4. The indium phosphide crystal substrate according to claim 1, wherein the main surface has a diameter not smaller than 100 mm and not greater than 101.6 mm, the indium phosphide crystal substrate contains sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 60 cm⁻².
 5. The indium phosphide crystal substrate according to claim 1, wherein the main surface has a diameter not smaller than 100 mm and not greater than 101.6 mm, the indium phosphide crystal substrate contains tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 2200 cm⁻² and not higher than 5000 cm⁻².
 6. The indium phosphide crystal substrate according to claim 1, wherein the indium phosphide crystal substrate contains iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁶ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².
 7. The indium phosphide crystal substrate according to claim 1, wherein the main surface has a diameter not smaller than 152.4 mm and not greater than 205 mm, the indium phosphide crystal substrate contains iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 2.0×10¹⁶ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².
 8. The indium phosphide crystal substrate according to claim 2, wherein the main surface has a diameter not smaller than 100 mm and not greater than 101.6 mm, the indium phosphide crystal substrate contains sulfur atoms at a concentration not lower than 5.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 500 cm⁻².
 9. The indium phosphide crystal substrate according to claim 2, wherein the main surface has a diameter not smaller than 100 mm and not greater than 101.6 mm, the indium phosphide crystal substrate contains sulfur atoms at a concentration not lower than 2.0×10¹⁸ cm⁻³ and not higher than 8.0×10¹⁸ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 10 cm⁻² and not higher than 60 cm⁻².
 10. The indium phosphide crystal substrate according to claim 2, wherein the main surface has a diameter not smaller than 100 mm and not greater than 101.6 mm, the indium phosphide crystal substrate contains tin atoms at a concentration not lower than 1.0×10¹⁸ cm⁻³ and not higher than 4.0×10¹⁸ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 2200 cm⁻² and not higher than 5000 cm⁻².
 11. The indium phosphide crystal substrate according to claim 2, wherein the indium phosphide crystal substrate contains iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 1.0×10¹⁶ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm⁻².
 12. The indium phosphide crystal substrate according to claim 2, wherein the main surface has a diameter not smaller than 152.4 mm and not greater than 205 mm, the indium phosphide crystal substrate contains iron atoms at a concentration not lower than 5.0×10¹⁵ cm⁻³ and not higher than 2.0×10¹⁶ cm⁻³, and the indium phosphide crystal substrate has an average dislocation density not lower than 500 cm⁻² and not higher than 5000 cm^(−2.) 